A roofing system generally includes a roof deck which is considered the structural supporting surface of a building extending between the surrounding exterior walls of the building. The roof deck may be constructed from plywood, metal decking or concrete or any other suitable material. Depending upon the construction, the roof deck may extend over the surrounding exterior walls or the roof deck may stop short of the exterior walls thereby forming a parapet wall, i.e., a low retaining wall at the edge of the roof deck. If desired, the roofing system may also include an insulation barrier formed from polyisocyanarate or any other suitable material applied over the roof deck.
To make the roof deck and building weather resistant a single-ply membrane roof is installed over the roof deck. The single-ply membrane roof refers to a water impermeable single sheet of polymeric material such as ethylene propylene diene rubber (EPDM) having a preapplied hot melt adhesive, chlorinated polyethylene, polyvinyl chloride, or chlorosulfanated polyethylene. The membrane roof has heretofore been installed on the roof deck using a variety of different methods.
For example, the field or interior of the membrane roof may be held to the roof deck by the use of ballast and/or penetrating or non-penetrating fastener means as known in the art. An example of a penetrating fastener means for retaining the field of a membrane roof installed to a roof deck is by utilizing a plurality of small, circular, metal plates having a hole in the center and a roofing screw or other suitable fastener. In order to anchor the membrane roof, the small, circular, metal plates are spaced apart in rows on the membrane roof and the fastener is driven through the hole in each plate, the membrane roof, any insulation material and then into the roof deck. The metal plates are then covered by overlapping roof membrane. An example of a non-penetrating fastener means would include totally adhering the field of the membrane roof to the roof deck.
An important consideration for a mechanically fastened membrane roof system is that the system withstand wind uplift forces. Consequently, in order to withstand wind uplift forces the membrane is typically fastened to the deck at close intervals over the entire membrane surface thereby minimizing the areas of membrane not secured to the roof deck. If the membrane sheets are secured only along the longitudinal edges the width of the membrane sheets should be restricted to a dimension of about 5-6 feet in order to ensure adequate resistance to uplift in the membrane between fastening locations.
Although the many known variations for attaching a membrane roof to a roof deck have been proven to perform satisfactorily under certain conditions, further improvements on attaching a membrane roof to a roof deck are desired.
One object of the present invention is to provide an inexpensive mechanically fastened single-ply roofing system of improved durability under a wide range of climatic conditions and improved resistance to wind uplift forces. Yet another object of the present invention is to provide an improved membrane roofing system which enables transferring to the membrane fabricating plant a substantial amount of the labor normally performed on the roof deck, thereby increasing efficiency and reducing labor costs, as well as assuring reliable product quality by providing better quality control. Another object of the present invention is to provide an improved method of securing a membrane roof to a roof deck in a manner which reduces labor and material costs but which does not decrease field performance. It is a further object of the present invention to provide an improved method of securing a membrane roof to a roof deck which permits the use of wider sheets of membrane thereby minimizing the total number of welded seams of the membrane sheets and/or mechanical fastening of the membrane sheets to the roof deck. Yet another object of the present invention is to provide a method of installing a membrane roof to a roof deck that is simple and economical.